A variety of engine performance monitoring and diagnostic routines have been proposed over the years. Most modern engines, and machines generally, have routine maintenance schedules where the engine or machine is brought in for service and various parts are tested, cleaned, inspected, repaired, and potentially replaced. On-board diagnostics and the like can enable operators and owners to be easily alerted to needed servicing prior to the next scheduled maintenance. Such diagnostics can also be of value in the validation of changed specifications or in analysis as to whether service intervals are in fact optimally scheduled.
Those skilled in the art will be familiar with the general desirability of scheduling routine maintenance relatively infrequently. In other words, since an engine is removed from service for a time whenever maintenance is needed, certain operations where the engine is ordinarily used may need to be idled or may otherwise be inconvenienced. Moreover, owners typically desire their machines to be operating as much of the time as is practicable. A typical example is an electrical power genset which can operate most of the hours of the day or continuously, but must be taken off-line for inspection and/or replacement of many different components. To be conservative, manufacturers typically schedule routine maintenance relatively frequently so as to prevent otherwise avoidable unscheduled downtime when unexpected breakdowns or the like occur. Improved diagnostics can improve engineers' understanding of when service is really needed, and can better warn operators and owners when something appears to be amiss outside of routine maintenance schedules. In the case of certain components and subsystems, such as engine electrical systems used in spark-ignited engines, it can be desirable to understand when sparkplug failure is expected prior to such failure actually occurring. Commonly owned United States Patent Application Publication No. 2015/0340846 to Schultz et al. is directed to a detection system for determining spark voltage. For example, Schultz et al. is directed to detecting a spark time based on a signal indicating that a voltage, on a low side of a primary coil, exceeds a threshold.